1. Field of the Invention
The invention relates to an image processing apparatus, an image processing method, and a computer program for correcting a color drift of ink which is caused when a color density decomposing process is executed to high concentration ink.
2. Related Background Art
Hitherto, a color separation image process of a color printer (hereinafter, referred to as an ink decomposing process) is constructed as shown in FIG. 7. The ink decomposing process will be described hereinbelow with reference to FIG. 7. In FIG. 7, reference numeral 701 denotes a luminance/density converting unit; 702 a UCR/BG processing unit; 703 a BG amount setting unit; and 704 a UCR amount setting unit. 8-bit data R′G′B′ as inputted luminance information is converted into concentration data CMY by the luminance/density converting unit 701 on the basis of the following equations.C=−α log(R′/255)   (1)M=−α log(G′/255)   (2)Y=−α log(B′/255)   (3)where, α: arbitrary real number
Subsequently, the CMY data is converted into the following data on the basis of β(Min(C, M, Y),μ) set into the BG amount setting unit 703 and a value μ% set into the UCR amount setting unit 704.C′=C(μ/100)*Min(C, M, Y)   (4)M′=M(μ/100)*Min(C, M, Y)   (5)Y′=Y(μ/100)*Min(C, M, Y)   (6)K′=β(Min(C, M, Y),μ)*(μ/100)*Min(C, M, Y)   (7)where, β(Min(C, M, Y),μ): real number which varies in dependence on Min(C, M, Y) and μ
A method of inserting K ink can be set on the basis of a value of β(Min(C, M, Y),μ). A UCR amount and a BG amount largely influence a color gamut of the color printer and granularity of the printer depending on the method of inserting the K ink (Japanese ink). Therefore, the UCR amount and the BG amount become parameters which are very important in the color separating process of the color printer (Japanese Patent Publication No. S62-050015).
In order to raise the granularity of the printer, CMYK data calculated as mentioned above is color-density-decomposed into ink of five colors or more including ink of Lm (light magenta), Lc (light cyan), Lk (light black), and the like which are made by diluting ink of C (cyan), M (magenta), K (black), and the like.
However, there is such a problem that if the color density decomposition of the ink is executed in the color density decomposing process of the color printer, the color obtained after the color density decomposition is drifted from that before the color density decomposition due to a difference of solvents constructing the ink, an influence of a material for increasing viscosity of the ink, and the like. Hitherto, correction of the color drift for such a problem is not considered.